One example of a conventionally-known driving apparatus is disclosed in Japanese Patent Application Laid-Open Publication No. 2011-72053, and includes a casing in which an electric motor is housed. In the casing of the driving apparatus disclosed in Japanese Patent Application Laid-Open Publication No. 2011-72053, a gear case and a cover are fixed to each other. An electric motor housed in the motor case has a stator and a rotor, and a rotating shaft is provided and rotated together with the rotor. A part of rotating shaft is fitted with a worm, and disposed in the gear case. A worm wheel is disposed in the gear case, and the worm wheel has a gear formed on a circumferential part of the worm wheel. The gear is engaged with the worm.
Additionally, the cover has an air hole which functions as an element for communicating the inside of the casing with the outside of the casing. The cover is fitted with a breather cap encircling the air hole. The breather cap functions as an element for ventilation through the air hole and for preventing a foreign substance from passing through the air hole. In the driving apparatus disclosed in Japanese Patent Application Laid-Open Publication No. 2011-72053, since the inside of the casing and the outside of the casing communicate with each other through the air hole, it is possible to suppress an increase in temperature difference and pressure difference between the inside of the casing and the outside of the casing.